Method for stabilization of heavy metals and odor control with dicalcium phosphate dihydrate powder

ABSTRACT

This invention provides a method for stabilization and treatment of heavy metal bearing materials and wastes subject to acid leaching tests or leach conditions and odor limits by addition of acid semi-soluble DiCalcium Phosphate DiHydrate such that the leaching potential is inhibited to desired levels and odors are reduced to desired levels and the material or waste is free flowing, more permeable, less weight and permits immediate handling and disposal or reuse. The resultant material or waste after stabilization is deemed suitable for on-site reuse, off-site reuse or disposal as RCRA non-hazardous waste.

BACKGROUND OF THE INVENTION

Over the past thirty years, the potential and observed dangers of heavymetal bearing materials and waste exposure to humans and the environmentand the generation of nuisance odors and from solid waste managementfacilities has been the basis of extensive regulatory control. Theleaching and transport of heavy metals into surface water bodies andgroundwater is a grave concern because of the danger that the drinkingwater supplies and the environment will become contaminated. Heavy metalbearing materials and wastes, such products or waste, paint residues,sludge, plating wastes, sediments, foundry dusts, casting sands, steelmill dusts, shredder residues, wire insulation, refuse incineratorflyash, incinerator bottom ash, incinerator combined ash, scrubberresidues from air pollution control devices such as cyclones,electrostatic precipitators and bag-house filter bags, may be deemedhazardous by the United States Environmental Protection Agency (U.S.EPA) pursuant to 40 C.F.R. Part 261 if containing certain soluble heavymetals above regulatory limits. Any solid waste can be defined ashazardous either because it is “listed” in 40 C.F.R., Part 261 Subpart Dor because it exhibits one or more of the characteristics of a hazardouswaste as defined at Part 261, Subpart C. These characteristics are: (1)ignitability, (2) corrosivity, (3) reactivity, and (4) toxicity astested under the Toxicity Characteristic Leaching Procedure (TCLP).Heavy metal bearing materials and wastes can also be regulated understate and federal groundwater and surface water protection standards,which set total and leachable limits for heavy metals often lower thanthe TCLP criteria, as the wastes and materials are not in a linedlandfill and exposed to direct groundwater, drinking water, storm watersand surface water bodies. The odor produced during management orstabilization of these wastes and materials, such as from refuseincinerator ash residues and operations that process ash residues, canbecome problematic for the operators of such facilities, as many wastegeneration and stabilization operations are nearby industrial,commercial and/or residential settings. Odor emissions are regulatedmostly under local ordinance rules of nuisance and some countries underfederal and/or state air quality regulations.

40 C.F.R., Part 261.24(a), contains a list of contaminants and theirassociated maximum allowable concentrations. The inorganic list includesAs, Ag, Ba, Cd, Cr, Pb, Hg, and Se. If a contaminant exceeds its maximumallowable concentration, when tested using TCLP analysis as specified at40 C.F.R. Part 261 Appendix 2, then the material is classified ashazardous. The TCLP test uses a dilute acetic acid either in de-ionizedwater (TCLP fluid 2) or in de-ionized water with a sodium hydroxidebuffer (TCLP fluid 1). Both extracts attempt to simulate the leachatecharacter from a decomposing trash landfill in which the hazardous wastebeing tested for is assumed to be disposed of in, and thus subject tothe acetic acid leaching condition. Waste containing leachable heavymetals is currently classified as hazardous waste due to the toxicitycharacteristic, if the level of TCLP analysis is above 0.2 to 100milligrams per liter (mg/L) or parts per millions (ppm) for definedmetals. The TCLP test is designed to simulate a worst-case leachingsituation, i.e., leachate which would typically be found in the interiorof an actively degrading municipal landfill. Such landfills normally areslightly acidic with a pH of approximately 5+0.5. Countries outside ofthe US also use the TCLP test as a measure of leachability such asTaiwan, Philippines, Thailand, and Canada. Thailand also limitssolubility of Cu and Zn, as these are metals of concern to Thailandgroundwater. Switzerland and most European countries also regulatemanagement of solid wastes by measuring heavy metals and salts as testedby a sequential leaching method using carbonated water simulating acidrainwater. Japan and the United Kingdom use similar carbonated DI waterleach tests to measure for landfill leaching potential from heavymetals.

Additionally, U.S. EPA land disposal restrictions prohibit the landdisposal of treated hazardous wastes that leach in excess of maximumallowable concentrations upon performance of the TCLP analysis. The landdisposal regulations require that hazardous wastes are treated until theheavy metals do not leach at Universal Treatment Standard (UTS) levelsfrom the solid waste at levels above the maximum allowableconcentrations prior to placement in a surface impoundment, waste pile,landfill or other land disposal unit as defined in 40 C.F.R. 260.10.

Communities have local ordinances that regulate the generation of odorsthat would be a public nuisance, and in some cases regulators haveestablished maximum allowable odor index levels. Maximum hourly averageand daily average chemical gas and particulate levels have also beenestablished under the US Clean Air Act and Amendments, and by OSHA andNIOSH. Odor Index Tests using varied levels of activated carbon mixedwith the subject waste or material and utilizing a panel of people withhuman olfactory sense is one method of comparing odors. The panel isasked to confirm or deny sense of odor, which is related to the amountof activated carbon used in the subject waste and generates an odorindex. The lower the index, the stronger the odor would be encountered.There may exist certain health and environmental release risks from theemission and transfer or diffusion of odor bearing gases, and thus theneed to control and reduce such odiferous gases may extend beyond asimple nuisance issue. H2S gas for example, having a rotten egg odor, ishighly toxic and can cause death in humans upon exposure to lower lethallevels at very low duration.

Leach tests subject solid wastes, including sludge, ash, residues,material or soil, to dilute acetic acid leaching (TCLP), buffered citricacid leaching (STLC), distilled water, synthetic rainwater (SPLP, MEP)or carbonated water leaching (Japanese, UK, Swiss, and USEPA SW-924).Synthetic rainwater leach tests are also often used to measure heavymetal solubility and compare such to groundwater and surface water stateand federal standards where materials and wastes are either reusedon-site or disposed in a manner other than lined landfills.

Suitable acetic acid leach tests include the USEPA SW-846 Manualdescribed Toxicity Characteristic Leaching Procedure (TCLP) andExtraction Procedure Toxicity Test (EP Tox) now used in Canada. Briefly,in a TCLP test, 100 grams of waste are tumbled with 2000 ml of diluteand buffered acetic acid for 18 hours. The extract solution is made upfrom 5.7 ml of glacial acetic acid and 64.3 ml of 1.0 normal sodiumhydroxide up to 1000 ml dilution with reagent water.

Suitable synthetic acid leach tests include the USEPA SW-846 Manualdescribed Synthetic Precipitant Leaching Procedure (SPLP) and MultipleExtraction Procedure Test (MEP) now used in the US for sites wherewastes are reused outside of leachate collected and lined landfills.Briefly, in a SPLP test, 100 grams of waste are tumbled with 2000 ml ofdilute nitric and sulfuric acid for 18 hours. The extract solution ismade up to pH at near 4.8 simulating acid rainwater East and West of theMississippi. The MEP is the Multiple Extraction Procedure which uses theTCLP type test for the first extract and followed by 9 cycles of theSPLP, all of which report leachate values, and thus attempt to measurediffusion potential of the waste matrix.

Suitable carbonated water leach tests include the Japanese leach testwhich tumbles 50 grams of composited waste sample in 500 ml of water for6 hours held at pH 5.8 to 6.3, followed by centrifuge and 0.45 micronfiltration prior to analyses. Another suitable distilled water CO2saturated method is the Swiss protocol using 100 grams of cemented wasteat 1 cm3 in two (2) sequential water baths of 2000 ml. The concentrationof heavy metals and salts are measured for each bath and averagedtogether before comparison to the Swiss criteria.

Suitable citric acid leach tests include the California Waste ExtractionTest (WET), which is described in Title 22, Section 66700,“Environmental Health” of the California Health & Safety Code. Briefly,in a WET test, 50 grams of waste are tumbled in a 1000 ml tumbler with500 grams of sodium citrate solution for a period of 48 hours. The heavymetal concentration is then analyzed by Inductively-Coupled Plasma (ICP)after filtration of a 100 ml aliquot from the tumbler through a 45micron glass bead filter.

Suitable odor measure test would be include activated carbon modifiedsamples with comparative olfactory measure of resultant odor by humanpanel.

Of specific interest and concern regarding the present invention is theleaching of individual heavy metal groups including As, Hg, Cd, Cr, Cu,and Pb and combinations thereof under TCLP, SPLP, MEP, CALWET, acidrainwater and acid rain derived surface water conditions and underregulatory tests which attempt to simulate dilute acid water leachingfor determination of hazardousness of incinerator ash residues. Inaddition, the reduction of odor generation from the handling andstabilization of ash is desired, as the processing and stabilization ofincinerator ash is often in close proximity to adjacent industrial,commercial and residential settings. In a specific case, incinerator ashmanagement and stabilization caused strong odors which in turn resultedin complaints to regulators, and thus the subject invention wasdeveloped to reduce odors and allow for stabilization.

The present invention provides a method of reducing the leachability ofmaterial or waste including the groups As, Hg, Cd, Cr, Cu, and Pb andcombinations thereof under TCLP, SPLP, MEP, CALWET, acid rainwater andacid rain derived surface water leaching conditions, and reduce sensibleodors generated during such stabilization, with use of dilute acidsemi-soluble DiCalcium Phosphate DiHydrate (DCPDH) [CaHPO4.2H2O]pulverized “seed” that minimize weight increase of the treated materialor waste and permit immediate stabilized matrix management and handlingwithout water application and mixing, without curing requirements andassociated double handling required from interim storage piles, andwhile producing a free-flowing and more permeable stabilized material orwaste suitable for excavator or loader loading, truck unloading and landdisposal or immediate reuse spreading and compaction. The presentinvention recognizes the use of dilute acids as leaching fluids to whichDCPDH will be added, and thus teaches use of a stabilizer that is diluteacid semi-soluble.

Unlike the present invention, prior art has taught stabilization ofheavy metals by addition of water soluble or water based physicalencapsulation agents, and have failed to recognize the value ofstabilizers which are not water soluble or have limited watersolubility, yet are semi-soluble or available in dilute acetic acid(TCLP), dilute sulfuric and nitric acid (SPLP/MEP) and dilute citricacid (CALWET), and failed to produce a stabilization process withreduction of odor production. In particular, O'Hara (U.S. Pat. No.4,737,356) and Forrester (U.S. Pat. Nos. 5,245,114 and 5,430,233) teachthe need to add water soluble phosphates to incinerator ash, autoshredder and wire insulation wastes, and incinerator bottom ash, whichare at least 5 gm/100 ml water solubility, with the preferred embodimentbeing 100% water soluble phosphoric acid, and which increases the odorsfrom incinerator ash. Prior art stabilization methods using Portlandcement, lime, cement kiln dust, phosphoric acids, and combinations alsoproduce a reduced permeability matrix or solid material form by addingwater (by combination or as part of the water soluble agent addition) tothe stabilization recipe for a chemical reaction which presentspost-stabilization handling and disposal complications, whereas thepresent invention use of pulverized DCPDH acts to reduce metalssolubility without significant reduction of waste permeability, withoutformation of cement-like non-free flowing material or waste, withoutcuring time, without water hydration and associated material and wasteweight increase, without double material and soil handling required forcuring stockpiles, thus permitting immediate stabilizer material orwaste handling, loading, disposal or reuse. The pulverized DCPDHsemi-soluble seed stabilization method operates on the basic principlethat sufficient wet dilute acid environment contact and mixing betweenthe material or waste and DCPCH will occur within the TCLP, SPLP, MEP orCALWET extraction vessel. Although the exact reason for odor reductionis not know at this time, it is postulated that the odors are reduceddue to the fine powder and neutral nature of DCPDH which acts as anadsorbent of organics and sulfides produced from ash. The extractionmethod(s) used to predict leaching potential all assume that fieldmaterial or waste disposal conditions are subject to hydration by acidrainwater or acid leachate and involve some degree of interstitialmixing of heavy metals with the extract fluid over some minimal periodof time in a saturated environment, and that such hydration can besimulated by an extract solute addition and mixing period. The DCPDHseed stabilization method thus utilizes the regulatory extractionprocedure to allow for post-stabilized material or waste hydration,mixing and wet chemistry dilute acid environment contact between heavymetals and DCPDH. The extraction tests thus act as dilute acid stirredtank reactors, which provide the opportunity for heavy metals on thesurface of materials and waste, and that which diffuses into the acidsolution, to have ample opportunity to contact DCPDH seeds that alsohave surface active and/or soluble mineral formation potentials with thedilute acid soluble and/or available heavy metals. Studies by theinventor found that the lower surface area non-pulverized forms of DCPDHwere less effective in reducing heavy metals solubility, which confirmedthat the surface area and semi-solubility of the exposed surface area ofDCPDH played an important role in the mineral formation potentials. Oneunique benefit of the dry seed technology is that SPLP, MEP, TCLP andCALWET extract fluid acid soluble and pulverized DCPDH can be applied towaste or material and dry mixed for uniformity in the field, andconsequently test samples of such stabilizers are allowed to freelytumble or mix in the presence of the heavy metals in the extractsolution for a given extraction period of time. This non-cemented andnon-reacted acid semi-soluble DCPDH pulverized surface mixing greatlyimproves the wet environment substitution of heavy metals such as Pb,Cd, Cr, Ni, and As into calcium phosphate apatite surfaces. Theextraction device effectively puts the heavy metals into solution aswell as some DCPDH into solution and remaining DCPDH surfaces into wetcontact and thus provides an excellent opportunity for surfacesubstitution, sorption and precipitation of now solution soluble andsolution face reactive heavy metals. Under this chemical mechanism, someor all stabilization agents are made available to the solution by theacid solution, and heavy metal ions are made available to the solutionwhich in turn substitute and exchange for calcium on insoluble apatitesurfaces and precipitate with stabilization agents in acid solution.

U.S. Pat. No. 5,202,033 describes an in-situ method for decreasing PbTCLP leaching from solid waste using a combination of solid wasteadditives and additional pH controlling agents from the source ofphosphate, carbonate, and sulfates.

U.S. Pat. No. 5,037,479 discloses a method for treating highly hazardouswaste containing unacceptable levels of TCLP Pb such as lead by mixingthe solid waste with a buffering agent selected from the groupconsisting of magnesium oxide, magnesium hydroxide, reactive calciumcarbonates and reactive magnesium carbonates with an additional agentwhich is either an acid or salt containing an anion from the groupconsisting of Triple Superphosphate (TSP), ammonium phosphate,diammonium phosphate, phosphoric acid, boric acid and metallic iron.

U.S. Pat. No. 4,889,640 discloses a method and mixture from treatingTCLP hazardous lead by mixing the solid waste with an agent selectedfrom the group consisting of reactive calcium carbonate, reactivemagnesium carbonate and reactive calcium magnesium carbonate.

U.S. Pat. No. 4,652,381 discloses a process for treating industrialwastewater contaminated with battery plant waste, such as sulfuric acidand heavy metals by treating the waste waster with calcium carbonate,calcium sulfate, calcium hydroxide to complete a separation of the heavymetals. However, this is not for use in a solid waste situation.

Unlike the present invention, however, none of the prior art solutionstaught specific dilute acid semi-soluble dry pulverized DCPDH seedstabilization of heavy metal bearing material or waste containing one ormore heavy metals while also forming a free-flowing, more permeablestabilized matrix suitable for loading, transport, disposal and reusewithout having a cement-like reduced permeability and strength, andwithout the burden of curing and associated double waste handling, andwithout reduction of odor. Specifically, prior art has failed to teachthe mechanism of acid semi-soluble and pulverized DCPDH seed to allowintentional leaching of heavy metals into the regulatory extractionvessel and subsequent substitution of such metals onto DCPDH surfacesand precipitation and complex formation with a certain acid semi-solubleamount of DCPDH in acid solution.

SUMMARY OF THE INVENTION

The present invention discloses a heavy metal bearing material or wastestabilization method through contact of material or waste with acidsemi-soluble DCPDH pulverized seed which complements the material orwaste leaching potential and desired free-flowing and more permeablematerial or waste handling characteristics without hydration, curing andassociated additional waste or material interim storage, handling,transport, disposal costs, and provides waste odor reduction. Ofspecific interest is the disclosure that pulverized DCPDH provides forheavy metal stabilization by surface substitution or by precipitationwith acid semi-soluble DCPDH during the regulatory extraction procedure.The DCPDH is provided in dry pulverized chemical form, and thus can becontacted with heavy metal bearing material either prior to wasteproduction such as in-stream at wastewater facilities producing sludgeor in-duct prior to air pollution control and ash collection devices orafter waste production in material collection devices or waste piles.

It is anticipated that pulverized DCPDH can be used for both RCRAcompliance actions such that generated wastes or materials fromwastewater facilities, furnaces, incinerators and other facilities donot exceed the TCLP hazardous waste criteria under TCLP or CERCLA(Superfund) response where stabilizers are added to waste piles orstorage vessels previously generated. The preferred method ofapplication of pulverized DCPDH would be in-line within the property andfacility generating the heavy metal bearing material, and thus allowedunder RCRA as a totally enclosed, in-tank or exempt method of TCLPstabilization without the need for a RCRA Part B hazardous wastetreatment and storage facility permit.

DETAILED DESCRIPTION

Environmental regulations throughout the world such as those promulgatedby the USEPA under CAA, RCRA and CERCLA require heavy metal bearingwaste and material producers to manage such materials and wastes in amanner safe to the environment and protective of human health, andreduce nuisance and toxic odor emissions. In response to theseregulations, environmental engineers and scientists have developednumerous means to control heavy metals and emissions, mostly throughchemical applications which convert the solubility of the material andwaste character to a low soluble form, thus passing leach tests andallowing the wastes to be either reused on-site or disposed at locallandfills without further and more expensive control means such ashazardous waste disposal landfills or facilities designed to providemetals stabilization, and odor and emissions reduction by air dilution,odor masking agents addition or gas destruction. The primary focus ofscientists has been on singular heavy metals such as lead, cadmium,chromium, arsenic and mercury, as these were and continue to be the mostsignificant mass of metals contamination in soils. Materials such aslead paints, incinerator ash, foundry and mill flyash, auto shredder andwire shredding residues and cleanup site wastes such as battery acidsand slag wastes from smelters are major lead sources. Recently, however,there exists a demand for control methods of process odor emissions andleaching of various heavy metals such as As, Hg, Cd, Cr, Pb, Cu andcombinations thereof in mining waste, wastewater sludge, shredderwastes, wire insulation, incinerator flyash, incinerator bottom ash,incinerator combined ash, foundry dusts, steel mill dusts, andcontaminated soils to meet nuisance regulations on odors and TCLP andalso SPLP, MEP, DI and other measures intended to measure fieldcondition leaching and/or solubility of the metals under digestion, in amanner which is rapid, low risk to workers, low impact on mechanicalprocess equipment, low cost, avoids interim storage and curing time, andpermits on-site or off-site reuse and handling at moisture levels belowor at optimum for compaction and handling.

The present invention discloses a heavy metal bearing material or wastestabilization method and odor reduction method through contact ofmaterial or waste with pulverized DCPDH acid semi-soluble stabilizingagent. The DCPDH found effective is available in dry pulverized form, aswell as less effective larger particle size particles, and thus can becontacted with heavy metal bearing material prior to waste generationsuch as in-stream at wastewater sludge producing plants or in-duct priorto air pollution control and ash collection devices or after wasteproduction in collection devices such as hoppers, dump valves,conveyors, dumpsters or waste piles. The DCPDH is applied dry, thusallowing stabilized material and waste to remain suitable for fillmaterial or loose handling and to remain less permeable thus allowingfor transmission of leachate or water flow. The transmission of waterflow becomes important an necessary when using the stabilized waste ormaterial as base fill, cover, embankment or engineered fill, thuseliminating damming or leachate production perched water table effects.

The acid semi-soluble pulverized DCPDH dry seed stabilization methodreduces the odor from waste and leachability of heavy metal bearingwastes including the groups As, Hg, Cd, Cr, Pb, and Cu and combinationsthereof under TCLP, SPLP, MEP, CALWET, DI, rainwater and surface waterleaching conditions as well as under regulatory water extraction testconditions as defined by waste control regulations in UK, Thailand,Japan, Switzerland, Germany, Sweden, the Netherlands and under AmericanNuclear Standards for sequential leaching of wastes, with use of acidsemi-soluble dry chemical pulverized DCPDH “seed” to minimize weightincrease of the treated waste and permit immediate stabilized matrixmanagement and handling without curing requirements or double handlingrequired for interim storage, and producing a free-flowing and morepermeable stabilized material or waste suitable for excavator or loaderloading, truck unloading and land disposal or immediate reuse spreadingand compaction.

The present invention provides a method of reducing the waste odors andleachability of material or waste including the groups As, Hg, Cd, Cr,Pb, and Cu and combinations thereof under TCLP, SPLP, MEP, CALWET, acidrainwater and acid rain derived surface water leaching conditions, withuse of dilute acid semi-soluble DCPDH pulverized seed that minimizesweight increase of the treated material or waste and permit immediatestabilized matrix management and handling without water application andmixing, without curing requirements and associated double handlingrequired from interim storage piles, and while producing a free-flowingand more permeable stabilized material or waste suitable for excavatoror loader loading, truck unloading and land disposal or immediate reusespreading and compaction. The present invention recognizes the use ofdilute acids as leaching fluids to which pulverized DCPDH will be added,and thus teaches use of a stabilizer that is dilute acid semi-soluble.

Unlike the present invention, prior art has taught stabilization ofheavy metals by addition of water soluble or water based physicalencapsulation agents, and have failed to recognize the value ofpulverized DCPDH which is not water soluble, yet is soluble and surfaceavailable in dilute acetic acid (TCLP), dilute sulfuric and nitric acid(SPLP/MEP) and dilute citric acid (CALWET). In particular, O'Hara (U.S.Pat. No. 4,737,356) and Forrester (U.S. Pat. Nos. 5,245,114 and5,430,233) teach the need to add water soluble phosphates to incineratorash, auto shredder and wire insulation wastes, and incinerator bottomash, which are at least 5 gm/100 ml water solubility, with the preferredembodiment being 100% water soluble phosphoric acid which increasesodors. Prior art stabilization methods using Portland cement, lime,cement kiln dust, phosphoric acids, and combinations also produce areduced permeability matrix or solid material form by adding water (bycombination or as part of the water soluble agent addition) to thestabilization recipe for a chemical reaction which presentspost-stabilization handling and disposal complications, whereas thepresent invention use of pulverized DCPDH acts to reduce odors andmetals solubility without significant reduction or increase ofpermeability, without formation of cement-like non-free flowing materialor waste, without curing time, without water hydration and associatedmaterial and waste weight increase, without double material and soilhandling required for curing stockpiles, thus permitting immediatestabilized material or waste handling, loading, disposal or reuse andmanagement in close proximity to residential and commercial operations.The pulverized DCPDH acid semi-soluble seed stabilization methodoperates on the basic principle that sufficient wet dilute acidenvironment contact and mixing between the material or waste and thepulverized DCPDH will occur within the TCLP, SPLP, MEP or CALWETextraction vessel. The extraction method(s) used to predict leachingpotential all assume that field material or waste disposal conditionsare subject to hydration by acid rainwater or acid leachate and involvesome degree of interstitial mixing of heavy metals with the extractfluid over some minimal period of time in a saturated environment, andthat such hydration can be simulated by an extract solute addition andmixing period. The pulverized DCPDH stabilization method thus utilizesthe regulatory extraction procedure to allow for post-stabilizedmaterial or waste hydration, mixing and wet chemistry dilute acidenvironment contact between heavy metals and pulverized DCPDH seed. Theextraction tests thus act as dilute acid stirred tank reactors, whichprovide the opportunity for heavy metals on the surface of materials andwaste, and that which diffuses into the acid solution, to have ampleopportunity to contact pulverized DCPDH seed that also has surfaceactive and/or semi-soluble mineral formation potentials with the diluteacid soluble and/or available heavy metals. One unique benefit of thepulverized DCPDH technology is that SPLP, MEP, TCLP and CALWET extractfluid acid semi-soluble pulverized DCPDH can be applied to waste ormaterial and dry mixed for uniformity in the field, and consequentlytest samples of such stabilizers are allowed to freely tumble or mix inthe presence of the heavy metals in the extract solution for a givenextraction period of time. This non-cemented and non-reacted acidsemi-soluble pulverized DCPDH surface mixing greatly improves the wetenvironment substitution of heavy metals such as Pb, Cd, Cr, and Cu intoDCPDH surfaces. The extraction device effectively puts the heavy metalsinto solution of suspension as well as acid semi-soluble pulverizedDCPDH into suspension and solution and thus provides an excellentopportunity for surface substitution, sorption and precipitation of nowsolution soluble heavy metals. Under this chemical mechanism, somepulverized DCPDH is made available to the solution by the acid solution,and heavy metal ions are made available to the solution which in turnsubstitute and exchange for calcium on insoluble DCPDH surfaces andprecipitate with certain semi-soluble DCPDH in the extract acidsolution.

It is anticipated that pulverized DCPDH, and fine particle DCPDH to aless effective degree, can be used for both RCRA compliance actions suchthat generated materials from mining operations, wastewater facilities,furnaces, incinerators and other facilities do not exceed appropriateTCLP hazardous waste criteria under TCLP, or used for CERCLA (Superfund)response where stabilizers are added to waste piles or storage vesselspreviously generated and now regulated under RCRA as a hazardous wastepre-disposal. The preferred method of application of DCPDH would be in apulverized form and in-line within the property and facility generatingthe heavy metal bearing material, and thus allowed under RCRA as atotally enclosed, in-tank or exempt method of TCLP stabilization withoutthe need for a RCRA Part B hazardous waste treatment and storagefacility permit(s).

DCPDH may also be used in combination with Portland cement, cement kilndust, lime kiln dust, silicates, lime, dolomitic lime, magnesium oxide,quicklime, phosphates, lime, ferric sulfate, ferrous sulfate, ferricchloride, iron powder, iron filings, chlorides, carbonates, monoammoniaphosphate (MAP), diammonium phosphate (DAP), single superphosphate(SSP), triple superphosphate (TSP), hexametaphosphate (HMP),tetrapotassium polyphosphate, dicalcium phosphate, tricalcium phosphate,monocalcium phosphate, phosphate rock, pulverized forms of all above dryphosphates, and combinations thereof depending on additional wastemanagement needs such as strength, permeability, odor control andadditional heavy metals control. In certain cases one may provideseveral additives such as iron, aluminum and other complexing agentswhich could also provide for a single-step formation of complexedapatites or low solubility minerals such as chloropyromorphite,plumbogummite or corkite. The stabilizer combination type, size, doserate, contact duration, and application means could be engineered foreach type of heavy metal bearing material or waste.

Although the exact stabilization formation molecule(s) are unknown atthis time, it is expected that when heavy metals comes into contact withthe pulverized DCPDH stabilizing agent in the presence of extractionfluids used during the extraction analyses, compound(s) begin to formsuch as a hydroxyapatites and phosphate metal precipitates throughmolecular substitution, aqueous precipitation, or surface sorption,which is less soluble than the heavy metal element or moleculeoriginally in the material or waste. Specifically complexing and/ortwinning of As, Hg, Pb, Cr, Cu, and Cd into pyromorphite and calciumapatites most likely occurs by adding DCPDH to the material or waste andwithin the extractor fluids at standard temperature and pressure. Theexact odor control method is not know at this time, but is expected toresult from the adsorptive nature and neutral pH range of the DCPDH. Italso remains possible that modifications to temperature and pressure mayaccelerate of assist formation of minerals, although such methods arenot considered optimal for this application given the need to limit costand provide for optional field based stabilizing operations that wouldbe complicated by the need for pressure and temperature control devicesand vessels.

Examples of suitable stabilizing agents include, but are not limited to,DiCalcium Phosphate DiHydrate (DCPDH) in pulverized form and variousfine particle form. The amounts of DCPDH agent used and the particlesize selected, according to the method of invention, depend on variousfactors including desired solubility reduction potential, odor controldesired, desired mineral toxicity, and desired mineral formationrelating to toxicological and site environmental control objectives. Ithas been found that an amount of 0.5% pulverized DCPDH by weight ofincinerator bottom ash waste, and 2.0% pulverized DCPDH by weight ofcombined incinerator ash, is sufficient for initial TCLP Pb and TCLP Pband Cd stabilization to less than RCRA limits of 5.0 and 1.0respectively and reduction of odor. However, the foregoing is notintended to preclude yet higher or lower usage of DCPDH or combinationswith other agents if needed, since it has been demonstrated that amountsgreater than 2% DCPDH by weight of waste also work, but are more costly.The examples below are merely illustrative of this invention and are notintended to limit it thereby in any way.

EXAMPLE 1

In this example refuse incinerator bottom ash was stabilized withvarying amounts of phosphoric acid (75% H3PO4) and DCPDH with zero (0)days of sample curing pre-TCLP extraction. Both stabilized andun-stabilized ash was subsequently tested for TCLP Pb, Cd, Cr, and Cuand ash product sensible odor. Samples were extracted according to TCLPprocedure set forth in Federal Register, Vol. 55, No. 126, pp.26985-26998 (Jun. 29, 199), which is hereby incorporated by reference.The leachate was digested prior to analysis by ICP. Phosphate mixturesproduced free flowing ash suitable for land disposal, passed the paintfilter test, with less than 20 PSI unconfined strength. Sample odor wastested by mixing ash with different levels of activated carbon andthereafter sensing odor by a panel of nine persons. The odor index ofeach sample was calculated by multiplying the average odor sense indexby 33 and producing a maximum odor index of 0 to 99. The lower thenumber index, the stronger the odor encountered by the panel.

TABLE 1 Stabilizer Dose (%) TCLP Cd/Pb/Cr/As (ppm) Odor Level 00.148/8.03/0.23/0.005 35.3 (Baseline) 0.4% H3PO4 0.140/0.80/0.48/0.03631.5 (Highest Odor) 0.4% DCPDH 0.09/0.73/<0.01/<0.01 69.2 (Least Odor)pulverized

The foregoing results in Table 1 readily established the operability ofthe present process to dry stabilize metals thus reducing leachabilityand odor while also producing wastes suitable for handling and disposalwithout curing time. Given the effectiveness of pulverized and fineparticle DCPDH in causing heavy metals to stabilize and reduce odor aspresented in the Table 1, it is believed that an amount of pulverizedDCPDH equivalent to less than 1% by weight of heavy metal bearingmaterial or waste should be effective.

While this invention has been particularly shown and described withreference to preferred embodiments thereof, it will be understood bythose skilled in the art that various changes in form and details may bemade therein without departing from the spirit and scope of theinvention as defined by the appended claims.

1. A method of reducing the leachability and odor of heavy metal bearingmaterial or waste, comprising contacting heavy metal bearing material orwaste with DiCalcium Phosphate DiHydrate in an amount effective inreducing the leaching of heavy metals from the material or waste to alevel no more than non-hazardous levels as determined in an EPA TCLPtest, performed on the stabilized material or waste, as set forth in theFederal Register, vol. 55, no. 126, pp. 26985-26998 (Jun. 29, 1990), andodor in accordance with odor index by olfactory measure.
 2. The methodof claim 1, wherein DCPDH is in pulverized or in fine particle form. 3.The method of claim 1 wherein As, Ag, Ba, Cd, Cr, Pb, Se, Hg, Sb, Cu, Niand Zn bearing material or waste is contacted with DCPDH in effectiveamount to reduce leaching to TCLP non-hazardous or desired levels andreduce odor to desired levels prior to collection of such material orwaste in containers.
 4. The method of claim 1 wherein As, Ag, Ba, Cd,Cr, Pb, Se, Hg, Sb, Cu, Ni and Zn bearing material or waste is contactedwith DCPDH in effective amount to reduce leaching to TCLP non-hazardousor desired levels and reduce odor to desired levels during or aftercollection of such material or waste in containers or during or aftergeneration of material or waste as a regulated waste.
 5. The method ofclaim 1 wherein the material of waste includes incinerator ash,incinerator bottom ash, incinerator combined ash, incinerator flyash,incinerator scrubber residue, shredder waste, shredder fluff, wireshredder insulation, contaminated soils, foundry sand, steel millflyash, slag, smelter ash, lead smelter ash, foundry flyash, leadprojectiles, lead projectile berm material, lead paint residue.
 6. Themethod of claim 1, wherein DCPDH is combined with cement kiln dust,Portland cement, silicates, lime, dolomitic lime, magnesium oxide,ferric chlorides, ferric sulfates, ferric ions, mineral complexingagents, and combinations thereof.
 7. A method of reducing theleachability and odor of combined heavy metal bearing material or waste,comprising contacting heavy metal bearing material or waste with DCPDHin an amount effective in reducing the leaching of combined heavy metalsfrom the material or waste to a level no more than non-hazardous ornon-acceptable levels as determined in SPLP, MEP, United Kingdom DI,Japan DI or Swiss sequential water leach test, performed on thestabilized material or waste, and reducing odor to desired levels. 8.The method of claim 7 wherein As, Ag, Ba, Cd, Cr, Pb, Se, Hg, Sb, Cu,Ni, and Zn bearing incinerator ash, foundry dust, smelter ash, smelterslag, shredder fluff, wire insulation, steel mill ash, is contacted withDCPDH in effective amount to reduce leaching to non-hazardous or desiredlevels and odor to desired levels prior to collection of such waste ormaterials in containers.
 9. The method of claim 7 wherein As, Ag, Ba,Cd, Cr, Pb, Se, Hg, Sb, Cu, Ni, and Zn bearing incinerator ash, foundrydust, smelter ash, smelter slag, steel mill ash, shredder fluff, wireinsulation, is contacted with at least on stabilizing agent in effectiveamount to reduce leaching to non-hazardous or desired levels and odorsto desired levels during or after collection of such waste or materialin containers or during or after generation as a regulated waste.